It depends on the type of language you want him to learn. For example, if he wants to learn VB, then you need to get the software to write and compile VB codes. Same thing applies to all other languages, Java, C#, etc.

It depends on the kind of game he wishes to make. If he wants to create something like whats on the shelf in gamestop, let him learn UnrealScript as a language. Get the UDK(google it) and WOTgreal(google). Thats what I use, i'm 14.